Home vegetable gardens often toxic, say researchers
The release of research findings highlights the need for home and community gardeners to have their garden soils tested for the presence of lead and other contaminants.
RESEARCH RESULTS on lead contamination in soils discloses many home garden soils are toxic and vegetables grown in them are likely to be contaminated with lead.
The Macquarie University research comes from analysis of 7256 soil samples from more than 3600 homes during its VegeSafe Program.
The research discloses:
- one-fifth of home vegetable gardens across Australia have soils with unsafe lead levels
- more than one-third of homes across Australia have garden soils exceeding the maximum 300mg/kg residential guidelines for lead contamination
- the percentage of gardens with toxic soils that pose a health risk to vegetable growers — Sydney, 31percent; Brisbane and Melbourne, 19 percent.
- leaf vegetables are at higher risk of lead contamination, root and fruiting vegetables less so.
In Sydney, the suburbs with the most contaminated soils are those in:
- the inner-city area
- Leichhardt
- Marrickville
- Ryde
- Burwood
- Strathfield.
Macquarie University’ s Professor Taylor identified sources of home soil contamination as timber houses where lead from paint used in the past persists in the soil, older homes with lead roof flashing and driplines.
There is higher risk in older inner-city homes and those near main roads where, prior to the phasing out leaded petrol, vehicle emissions deposited lead particulates in dust, soil and ceilings.
Lead contamination of garden soils is not restricted to urban areas. Older homes in country towns and farmhouses may also have contaminated garden soils. The findings raise the question of harvesting rainwater from the roofs of older homes with lead roof flashing and using it for human consumption. Usually, governments do not recommend drinking tank water or using it for cooking because of the risk of contmaination, including by bird and possum droppings. Some modern water pumps with ceramic filters and ultraviolet treatment of water may remove most contaminants.
The federal Department of Agriculture, Water and the Environment reports that “the amount of lead in Australia’s air has decreased significantly since the introduction of unleaded petrol in 1986. Before the phase-out of leaded petrol, which began in 1993, the national air quality standard for lead was regularly exceeded in urban environments. Levels are now less than 10 per cent of the national annual standard of 0.5 micrograms per cubic metre of air.”
Alarm over lead-contaminated home vegetable garden soil has been raised before. A 2018 report in Australian Food News disclosed that “RMIT researchers tested 136 veggie patches in Melbourne’s metropolitan area, finding one-in-five were contaminated with high levels of lead exceeding Australian safety guidelines.
“The older the house, the more lead generally found in the garden soil. We found that the concentration of lead in soil was higher in painted homes, and in soil underneath the dripline.”
The researchers said home vegetable growers should get their soils tested for lead contamination.
Mitigating food contamination
To mitigate the health risk to gardeners and their families, Professor Taylor suggests:
- growing vegetables in raised beds using fresh, clean soil; raised beds lift the vegetable root zone above the soil below the beds
- mulching exposed soil
- preventing transference of contaminated soil and dust into the house by removing shoes before entering
- keeping pets — a vector of contamination — either inside or outside
- washing hands
- creating a clean outdoor play space for children, including garden beds made with clean, purchased soil.
Gardening can raise dust, so there is potential for the dust to carry lead particles. Some gardeners wear a mask when working in dusty conditions and when spreading mulch, so perhaps that could prevent inhalation of lead particles.
Health impacts accumulate
Lead bioaccumulates in the human body — it builds up over time.
The World helath Organisation (WHO) says lead enters the brain, liver, kidney and bones. It accumulates in teeth and bones over time. Lead in bone is released into blood during pregnancy and becomes a source of exposure to the developing fetus.
There is no level of exposure to lead that is known to be without harmful effects, says WHO.
